Authorities in Belgium have launched a criminal investigation into a group of doctors who euthanised a 38-year-old woman with autism.

Tine Nys was euthanised in 2010 two months after she was diagnosed with Asperger's syndrome but her family question the speed with which the diagnosis was made and allege numerous irregularities in her death.

According to the Brussels Times, the family's formal complaint also claimed that the life-ending drugs had been administered in an 'amateurish' way.

The three doctors from East Flanders are to now stand trial on suspicion of poisoning in the first euthanasia case to go to trial in Belgium since the practice was made legal in 2002.

Among those to stand trial over Nys' death is her psychiatrist Dr Lieve Thienpont, who approved the euthanasia.

Brother Rene Stockman, the head of a Catholic order that runs psychiatric homes in Belgium has welcomed the prosecutions, saying euthanasia in the country was 'uncontrolled'.

'We all know that Belgium is on the top with a very liberal law on euthanasia, even for minors and psychiatric patients,' he said.

'We can only hope that this case will invite people to reflect which way they are going with society, where absolute freedom and autonomy and self-determination have become absolute number one on the scale of values.'

The law in Belgium permits euthanasia for those in 'unbearable suffering', both physical or mental. It is one of the most liberal laws in the world, allowing children of any age to request euthanasia so long as they have the mental capacity to do so and parental consent.

Earlier this year, a report from the commission that regulates euthanasia in Belgium revealed that it had become the first country in the world to euthanise children under the age of 12.

The report said that a nine-year-old with a brain tumor and an 11-year-old suffering from cystic fibrosis had been euthanised in the country in either 2016 or 2017. A third minor, a 17-year-old suffering from muscular dystrophy, had also received a lethal injection in the two-year period.